Braking apparatus

ABSTRACT

A braking system for a vehicle wheel which system comprises a reservoir, and a pump pumping liquid from the reservoir through a conduit and back to the reservoir in relation to the vehicle wheel speed. A progressively closable restriction is provided downstream of a connection to the brakes so liquid pressure upstream of the closable restriction may be increased to apply the brakes. A leakage conduit is provided to by-pass the closable restriction and the connection, and incorporates a variable restriction the opening of which increases with increased vehicle wheel speed.

United States Patent Hodge [54] BRAKING APPARATUS [72] Inventor: PeterCharles Hodge, London, England [73] Assignee: Simms Group Research andDevelopment Limited, London, England [22] Filed: Mar. 4, 1970 [2|] Appl.No.: 16,286

[30] Foreign Application Priority Data Mar. 6, 1969 Great Britain ..11902/69 52 use: ..303/2lF,303/l0,303/40, 303/61 511 Int.Cl. ..B60t8/065s FieldofSearch ..l88/l8l;303/2l,24,6,l0, 303/61-63, 68-69, 40

[56] References Cited UNITED STATES PATENTS 3,124,220 3/1964 Kell..303/l0 UX 51 May 9, 1972 3,032,995 5/ i962 Knowles ..303/l 0 X3,539,227 l 1/1970 Drutchas et al.... 3,524,684 8/ l 970 Skoyles3,514,162 5/1970 Erlebach et al ..303/l0 X Primary liraminer-MiltonBuchler .-lsrisrmu Brominer-John J. McLaughlin .-lnorm' \'Wuts0n. Cole.Grindle & Watson ABSTRACT A braking system for a vehicle wheel whichsystem comprises a reservoir, and a pump pumping liquid from thereservoir through a conduit and back to the reservoir in relation to thevehicle wheel speed. A progressively closable restriction is provideddownstream of a connection to the brakes so liquid pressure upstream ofthe closable restriction may be increased to apply the brakes. A leakageconduit is provided to by-pass the closable restriction and theconnection, and incorporates a variable restriction the opening of whichincreases with increased vehicle wheel speed.

7 Claims, 1 Drawing Figure BRAKING APPARATUS This invention relates tobraking systems, and provides a vehicle braking system comprising brakeoperating means, a pump having a liquid throughput-adapted to increasewith wheel rotational speed and arranged to withdraw liquid from areservoir and return it thereto after Circulation through a conduithaving a connection to the brake operating means, brake applying meanslocated downstream of the connection and operable to add a restrictioninto the conduit and arranged so that the liquid pressure in theconnection is increased, and a leakage path bypassing the brake applyingmeans, the leakage path incorporating means providing a resistance toliquid flow which decreases automatically with increased wheelrotational speed.

The leakage path may comprise a variable restriction in series with afixed restriction.

There may be provided means to sense the output provided by the liquidpump and means controlled by the sensing means to alter the variablerestriction.

In the above arrangement, the means to sense the output of the liquidpump may comprise a furtherrestriction in the main delivery path fromthe pump, and the altering means for the variable restriction maycomprise a shuttle arranged with the two sides of the shuttle open tothe pressure at the two sides of the further restriction respectively.

The shuttle may be in the leakage path, and may provide in combinationwith its cylinder the variable restriction.

ln any of the above arrangements, there may be damping means so that thevariation of the liquid resistance is arranged to lag the variation ofthe vehicle wheel speed.

The brake applying means may comprise a control valve arranged toprogressively restrict the flow of liquid from the pump in a return lineto the reservoir to increase the pressure in the connection to the brakeoperating means.

Reference is now made to the accompanying drawing which illustrates anembodiment of the present invention here given by way of example for aninstallation in connection with a wheel of a vehicle with a view toavoiding wheel lock on braka. brake pedal of the vehicle is indicated atl and this is connected through a link to a master cylinder of brakefluid shown at 3 which, on depression of pedal 1, pumps fluid through aline 2 to a cylinder 4. In the cylinder 4 there is a reciprocable valvemember 5 in fluid tight relationship with the bore of the cylinder, andtraversing the valve member 5 is an axial conduit 6 extending from theend of the member 5 adjacent line2 and emerging into radial portionscommunicating with an annulus 7. The valve member 5 has a taperedportion 8 provided at its other end, there being a spring 9 housed inthe end part of the cylinder 4 acting on the tapered portion 8 to urgethe member 5 towards the other end of the cylinder. The annulus 7co-operates, for a range of movement of the valve member 5, with aconduit 10 which leads to a further conduit 11 and thence to the brakecircuit of a wheel 12.

A tank 13 containing brake fluid has a filter 14 disposed transverselyacross it. A pump 15, having a throughput substantially proportional towheel speed and independent of output pressure over the operating speedand pressure range of the braking system, such as a transfer, piston orgear pump, is connected to the'tank l3 drawing fluid from one side ofthe filter, and pumps fluid under pressure through conduit 16. The pump15 is connected for rotation in dependence upon speed of rotation ofwheel 12 and generates flow at the lowest rotational speeds of thewheel. A sensing restriction 17 in conduit 16 results in a differentialpressure as between a conduit 18 and a' conduit 19 connecting into theconduit 16 on each side respectively of the restriction 17, the conduits18 and 19 being connected to each end respectively of a control valvedevice indicated at 20. The conduit 18 is provided with a restriction 36or an elongated restriction 34 as shown in the inset drawing for apurpose described below. The conduit 19 leads to an axial bore 21 in ashuttle 22 housed in a sleeve member or housing in fluid tightrelationship therewith.

Towards the right hand side of the shuttle 22 in the drawing there aretapered flats 23 providing a variable restriction as hereinafterdescribed. A spring 24 biasses the shuttle 22 towards the right handside of the sleeve member (in the drawing). The sleeve member has anannular groove 25 disposed part way between its ends, to which there isconnected a conduit 26. In the conduit 26 there is indicated arestriction 27 which provides a main restriction as hereinafterdescribed. With movement of the shuttle 22 to the left in the drawingthere is a passage from conduit 19, through axial bore 21, thence pastflats 23 to annular groove 25 and thence to conduit 26 throughrestriction 27. The conduit 28 connects back to the tank 13' on theother side of the filter l4. Connection is made fromconduit 16 upthrough conduit 29 to the lower end of a cylinder 30 in which is locatedplug 31 biassed by a spring 32 to the position shown in the drawing.Conduit 29 is connectible with conduit 28 via conduit 33 in which latterconduit is located the tapered portion 8 and cylinder 4. When taperedportion 8 of valve member 5 does not obstruct conduit 33, i.e. beforedepression of, or on initial depression of brake pedal 1, the conduit 29is in communication with the conduit 28. Beyond this initial range ofdepression, connection from conduit 33 to conduit 28 is obstructed atleast in part by the tapered portion 8 of valve member 5. A relief valvedevice of conventional design is indicated at 35 and connects conduit 29to conduit 28.

With the device mounted in a vehicle the pump 15 generates a flow inconduit 16 in dependence upon rotational speed of wheel 12. Depressionof the brake pedal I initially results in fluid pressure from the mastercylinder 3 being applied via conduit 6, annulus 7, conduit 10 to theconduit 11 and thence to the brake circuit of the wheel 12. Thiscondition operates as long as annulus 7 co-operates with the conduit 10i.e. for an initial range of movement of brake pedal 1 as mentionedabove. During this initial range of movement of brake pedal 1, fluid fedto conduit 16 by pump 15 has a connection via conduit 29, conduit 33, toconduit 28, not being then obstructed by tapered portion 8, back to tank13.

With an extent of depression for the brake pedal 1 beyond this initialrange, the radial portions from the conduit 6 no longer co-operate withthe conduit 10. Also the tapered portion 8 of the valve member 5 then atleast partly obstructs the connection between conduit 33 and conduit 28.Fluid pressure then generated by the pump 15 in conduit 16 is appliedvia conduit 29, cylinder 30, to plug 31, which is displaced topressurize the fluid in the brake circuit of the wheel 12 and thus applythe brakes. This generated pressure in conduit 28 can leak back viaconduit 28 to tank 13 byvirtue of the leakoff path provided throughconduit 19. in this leak-off path back via conduit 19 there is a mainrestriction 27 and a variable restriction, past the tapered flats 23, independence upon the axial position of shuttle 22 in its housing. Thevariable restriction, created by the tapered flats 23 in variablecommunication with the annulus 25, is in series with the mainrestriction 27, in the leak-off path.

With high rotational wheel speeds a relatively high differentialpressure is generated by pump 15 across restriction 17. Highdifferential pressure forces shuttle 22 towards the left hand side ofits housing and the relatively large extent of opening then provided byflats 23 in communication with annulus 25 renders the main restriction27 relatively unaffected by the variable'restriction, in series with it.At low rotational wheel speeds, the shuttle'22 is urged by the spring 24towards the right since only a low differential pressure is generatedacross restriction 17. The variable restriction, in series with the mainrestriction 27 is then the dominant restriction and controls theleak-off path.

The response or movement of the shuttle 22 in its housing to pressurechanges caused by the differential pressure generated by restriction 17is controlled by the restriction 36 (or. 34). During transient speedchanges of the wheel and hence the pump the shuttle 22 is caused to takeup positions which are at a variance with the steady state positions.This has the effect of changing the rate at which pressures in conduit29 change.

The main restriction 27 can be incorporated into the sleeve member. Theshuttle 22 and sleeve member in which it is housed can be disposedtransversely or angularly with respect to the direction of travel of thevehicle to avoid acceleration effects on the operation of the shuttle22.

it has been found that a combination of variable restriction and mainrestriction as hereinbefore described helps avoid lock of vehicle wheelsand retention of braking performance over a range of wheel speeds,whereas the use of a fixed leakoff restriction tended towards avoidanceof wheel lock rather at singular values of wheel speed.

The above described apparatus may be duplicated for each wheel of avehicle, the pedal 1 and master cylinder 3 only being common to eachsystem. Alternatively, the system may be applied to pairs of wheels. Thepump 15 may be driven directly by a wheel, or by some other part of thetransmission.

in the above described embodiment, the response of the shuttle 22 tochanges in pressure across the restriction 17 is delayed by arestriction 36 or 34 in the conduit 18. Alternatively, the restriction36 or 34 may be omitted, in which case the inertia of the shuttle itselfcauses sufiicient delay to its response to the pressure across therestriction l7.

It will be appreciated that the effect of the damping means on thevariable restriction will cause the restriction to close completelyunder steady state conditions at very low rotational speeds of thewheel, but under dynamic conditions for instance if the wheel lockssuddenly when braking the restriction will not completely close to allowfluid leakage and thus at least partly release the brakes since the flowgenerated by the pump will have ceased.

lclaim:

l. A braking system for a vehicle wheel, comprising;

a. brake operating means;

b. a reservoir for liquids;

c. a pump having drive means which increases the pump throughput withincreased wheel rotational speed;

d. means to connect the pump input with the reservoir;

e. a conduit connecting the pump output with the reservoir;

f. a connection between the conduit and the brake operating means;

g. brake applying means located downstream of the connection, andoperable to add a restriction into the conduit so that the liquidpressure in the connection is increased;

h. a leakage conduit arranged to bypass the brake applying means, whichleakage conduit incorporates a variable restriction to provide avariable restriction to liquid flow and a fixed restriction in serieswith the variable restriction; and

i. means to vary the variable restriction automatically with increasedwheel rotational speed.

2. A braking system as claimed in claim 1 in which there is means tosense the throughput of the pump, which sensing means controls the meansto vary the variable restriction.

3. A braking system as claimed in claim 2 in which the means to sensethe throughput of the pump consists of a further restriction in theconduit upstream of the connection, and the varying means comprises ashuttle mounted in a cylinder and having two sides, each side beingconnected through further conduits to the pressure at the two sidesrespectively of the further restriction.

4. A braking system as claimed in claim 3 in which the shuttle isarranged in the leakage conduit, the shuttle in combination with itscylinder providing the variable restriction.

5. A braking system as claimed in claim 3 in which there is provideddamping means arranged so that the variation of the variable restrictionlags the variation of the vehicle wheel speed, which damping meanscomprises a damping restriction arranged in the further conduit betweenone side of the shuttle and the high pressure side of the furtherrestriction, so that movement of the shuttle and hence the variation ofthe variable restriction lags the variation of the vehicle wheel s ed.

. A braking system as claimed in claim 1 in which t e brake applyingmeans comprise;

a. a second liquid pump;

b. a brake actuating member connected to the second pump so thatmovement of the member produces an output from the second pump;

c. a control valve having a valve member progressively movable betweentwo positions;

d. a conduit connecting the output of the second pump to the controlvalve so that an output from the second pump moves the valve member;

e. a first conduit through the control valve which first conduitconnects the output of the second pump to the brake operating means whenthe valve member is in the first position; and

f. means on the valve member to progressively restrict the conduit fromthe first-mentioned pump downstream of the connection as the valvemember is moved progressively from its first position towards its secondposition.

7. A braking system for a vehicle wheel, comprising:

a. brake operating means;

b. a reservoir for liquids;

c. a pump having drive means which increases the pump throughput withincreased wheel rotational speed;

d. means to connect the pump input with the reservoir;

e. a conduit connecting the pump output with the reservoir;

f. a connection between the conduit and the brake operating means;

g. brake applying means located downstream of the connection, andoperable to add a restriction into the conduit so that the liquidpressure in the connection is increased;

h. a leakage conduit arranged to bypass the brake applying means, whichleakage conduit incorporates a variable restriction to provide avariable restriction to liquid flow;

i. means to vary the variable restriction automatically with increasedwheel rotational speed; and

j. damping means arranged so that the variation of the variablerestriction lags the variation of the vehicle wheel speed.

$ i i i

1. A braking system for a vehicle wheel, comprising; a. brake operatingmeans; b. a reservoir for liquids; c. a pump having drive means whichincreases the pump throughput with increased wheel rotational speed; d.means to connect the pump input with the reservoir; e. a conduitconnecting the pump output with the reservoir; f. a connection betweenthe conduit and the brake operating means; g. brake applying meanslocated downstream of the connection, and operable to add a restrictioninto the conduit so that the liquid pressure in the connection isincreased; h. a leakage conduit arranged to bypass the brake applyingmeans, which leakage conduit incorporates a variable restriction toprovide a variable restriction to liquid flow and a fixed restriction inseries with the variable restriction; and i. means to vary the variablerestriction automatically with increased wheel rotational speed.
 2. Abraking system as claimed in claim 1 in which there is means to sensethe throughput of the pump, which sensing means controls the means tovary the variable restriction.
 3. A braking system as claimed in claim 2in which the means to sense the throughput of the pump consists of afurther restriction in the conduit upstream of the connection, and thevarying means comprises a shuttle mounted in a cylinder and having twosides, each side being connected through further conduits to thepressure at the two sides respectively of the further restriction.
 4. Abraking system as claimed in claim 3 in which the shuttle is arranged inthe leakage conduit, the shuttle in combination with its cylinderproviding the variable restriction.
 5. A braking system as claimed inclaim 3 in which there is provided damping means arranged so that thevariation of the variable restriction lags the variation of the vehiclewheel speed, which damping means comprises a damping restrictionarranged in the further conduit between one side of the shuttle and thehigh pressure side of the further restriction, so that movement of theshuttle and hence the variation of the variable restriction lags thevariation of the vehicle wheel speed.
 6. A braking system as claimed inclaim 1 in which the brake applying means comprise; a. a second liquidpump; b. a brake actuating member connected to the second pump so thatmovement of the member produces an output from the second pump; c. acontrol valve having a valve member progressively movable between twopositions; d. a conduit connecting the output of the second pump to thecontrol valve so that an output from the second pump moves the valvemember; e. a first conduit through the control valve which first conduitconnects the output of the second pump to the brake operating means whenthe valve member is in the first position; and f. means on the valvemember to progressively restrict the conduit from the first-mentionedpump downstream of the connection as the valve member is movedprogressively from its first position towards its second position.
 7. Abraking system for a vehicle wheel, comprising: a. brake operatingmeans; b. a reservoir for liquids; c. a pump having drive means whichincreases the pump throughput with increased wheel rotational speed; d.means to connect the pump input with the reservoir; e. a conduitconnecting the pump output with the reservoir; f. a connection betweenthe conduit and the brake operating means; g. brake applying meanslocated downstream of the connection, and operable to add a restrictioninto the conduit so that the liquid pressure in the connection isincreased; h. a leakage conduit arranged to bypass the brake applyingmeans, which leakage conduit incorporates a variable restriction toprovide a variable restriction to liquid flow; i. means to vary thevariable restriction automatically with increased wheel rotationalspeed; and j. damping means arranged so that the variation of thevariable restriction lags the variation of the vehicle wheel speed.